Hydraulic actuated cavitation chamber with integrated fluid rotation system

ABSTRACT

A method for forming and imploding stabilized cavities within a cavitation chamber is provided. A hydraulically actuated piston is withdrawn to form the desired cavities and then extended to implode the cavities. At least one impeller is rotated in order to stabilize the cavities, the impeller being located within the cavitation chamber and magnetically coupled to an external drive system.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/068,080, filed Feb. 28, 2005 and No. 11/057,347, filed Feb.14, 2005, which is a continuation-in-part of Ser. No. 11/038,344, filedJan. 18, 2005, the disclosures of which are incorporated herein byreference for any and all purposes.

FIELD OF THE INVENTION

The present invention relates generally to cavitation systems and, moreparticularly, to a method for cavitating stabilized bubbles within acavitation chamber using a hydraulic actuated piston.

BACKGROUND OF THE INVENTION

Sonoluminescence is a well-known phenomena discovered in the 1930's inwhich light is generated when a liquid is cavitated. Although a varietyof techniques for cavitating the liquid are known (e.g., sparkdischarge, laser pulse, flowing the liquid through a Venturi tube), oneof the most common techniques is through the application of highintensity sound waves.

In essence, the cavitation process consists of three stages; bubbleformation, growth and subsequent collapse. The bubble or bubblescavitated during this process absorb the applied energy, for examplesound energy, and then release the energy in the form of light emissionduring an extremely brief period of time. The intensity of the generatedlight depends on a variety of factors including the physical propertiesof the liquid (e.g., density, surface tension, vapor pressure, chemicalstructure, temperature, hydrostatic pressure, etc.) and the appliedenergy (e.g., sound wave amplitude, sound wave frequency, etc.).

Although it is generally recognized that during the collapse of acavitating bubble extremely high temperature plasmas are developed,leading to the observed sonoluminescence effect, many aspects of thephenomena have not yet been characterized. As such, the phenomena is atthe heart of a considerable amount of research as scientists attempt tofurther characterize the phenomena (e.g., effects of pressure on thecavitating medium) as well as its many applications (e.g.,sonochemistry, chemical detoxification, ultrasonic cleaning, etc.).

Acoustic drivers are commonly used to drive the cavitation process. Forexample, in an article entitled Ambient Pressure Effect on Single-BubbleSonoluminescence by Dan et al. published in vol. 83, no. 9 of PhysicalReview Letters, the authors use a piezoelectric transducer to drivecavitation at the fundamental frequency of the cavitation chamber. Theyused this apparatus to study the effects of ambient pressure on bubbledynamics and single bubble sonoluminescence.

U.S. Pat. No. 4,333,796 discloses a cavitation chamber that is generallycylindrical although the inventors note that other shapes, such asspherical, can also be used. It is further disclosed that the chamber iscomprised of a refractory metal such as tungsten, titanium, molybdenum,rhenium or some alloy thereof and the cavitation medium is a liquidmetal such as lithium or an alloy thereof. Surrounding the cavitationchamber is a housing which is purportedly used as a neutron and tritiumshield. Projecting through both the outer housing and the cavitationchamber walls are a number of acoustic horns, each of the acoustic hornsbeing coupled to a transducer which supplies the mechanical energy tothe associated horn. The patent discloses that the temperatures achievedby a collapsing bubble depend strongly on whether or not the interfaceof the bubble and the host liquid remain spherical during collapse.Noting that the earth's gravitational field is an asymmetric force thatcan cause bubble deformation, the patent discloses that a preferredcavitation chamber includes means for applying a magnetic field tocancel the gravitational force, thus creating a zero-gravity fieldwithin the cavitation zone. U.S. Pat. No. 4,333,796 further disclosesthat if the bubble is cylindrical or quasi-cylindrical, small surfaceperturbations will neither grow nor decay. The patent discloses severalmeans of achieving such a bubble shape, including imposing atime-varying magnetic field.

U.S. Pat. No. 4,563,341, a continuation-in-part of U.S. Pat. No.4,333,796, discloses the use of a vertical standing pressure waveexcited by a transducer in the bottom wall of the chamber as a means ofreducing the effects of the earth's gravitational field within thecavitation zone.

U.S. Pat. No. 5,658,534 discloses a sonochemical apparatus consisting ofa stainless steel tube about which ultrasonic transducers are affixed.The patent provides considerable detail as to the method of coupling thetransducers to the tube. In particular, the patent discloses atransducer fixed to a cylindrical half-wavelength coupler by a stud, thecoupler being clamped within a stainless steel collar welded to theoutside of the sonochemical tube. The collars allow circulation of oilthrough the collar and an external heat exchanger. The abutting faces ofthe coupler and the transducer assembly are smooth and flat. The energyproduced by the transducer passes through the coupler into the oil andthen from the oil into the wall of the sonochemical tube.

U.S. Pat. No. 5,858,104 discloses a shock wave chamber partially filledwith a liquid. The remaining portion of the chamber is filled with gaswhich can be pressurized by a connected pressure source. Acoustictransducers mounted in the sidewalls of the chamber are used to positionan object within the chamber while another transducer delivers acompressional acoustic shock wave into the liquid. A flexible membraneseparating the liquid from the gas reflects the compressional shock waveas a dilatation wave focused on the location of the object about which abubble is formed.

U.S. Pat. No. 5,994,818 discloses a transducer assembly for use withtubular resonator cavity rather than a cavitation chamber. The assemblyincludes a piezoelectric transducer coupled to a cylindrical shapedtransducer block. The transducer block is coupled via a central threadedbolt to a wave guide which, in turn, is coupled to the tubular resonatorcavity. The transducer, transducer block, wave guide and resonatorcavity are co-axial along a common central longitudinal axis. The outersurface of the end of the wave guide and the inner surface of the end ofthe resonator cavity are each threaded, thus allowing the wave guide tobe threadably and rigidly coupled to the resonator cavity.

PCT Application No. US95/15972 discloses a non-periodically forcedbubble fusion apparatus. The apparatus is comprised of a liquid-filledpressure vessel into which deuterium gas bubbles are injected. Anon-periodic pressure field is generated within the liquid, the pressurefield causing the bubbles to oscillate and become compressed therebyheating the bubbles to a temperature which is sufficiently high to causea fusion reaction in the hot deuterium plasma formed at implosionstagnation. The application does not disclose any means of stabilizingthe movement of the injected bubbles or positioning the bubbles withinthe pressure vessel.

PCT Application No. US02/16761 discloses a nuclear fusion reactor inwhich at least a portion of the liquid within the reactor is placed intoa state of tension, this state of tension being less than the cavitationthreshold of the liquid. In at least one disclosed embodiment, acousticwaves are used to pretension the liquid. After the desired state oftension is obtained, a cavitation initiation source, such as a neutronsource, nucleates at least one bubble within the liquid, the bubblehaving a radius greater than a critical bubble radius. The nucleatedbubbles are then imploded, the temperature generated by the implosionbeing sufficient to induce a nuclear fusion reaction.

PCT Application No. CA03/00342 discloses a nuclear fusion reactor inwhich a bubble of fusionable material is compressed using an acousticpulse, the compression of the bubble providing the necessary energy toinduce nuclear fusion. The nuclear fusion reactor is spherically shapedand filled with a liquid such as molten lithium or molten sodium. Apressure control system is used to maintain the liquid at the desiredoperating pressure. To form the desired acoustic pulse, apneumatic-mechanical system is used in which a plurality of pistonsassociated with a plurality of air guns strike the outer surface of thereactor with sufficient force to form a shock wave within the liquid inthe reactor. The application discloses releasing the bubble at thebottom of the chamber and applying the acoustic pulse as the bubblepasses through the center of the reactor. A number of methods ofdetermining when the bubble is approximately located at the center ofthe reactor are disclosed.

In a paper entitled Sonoluminescence and Bubble Dynamics for a Single,Stable, Cavitation Bubble (J. Acoust. Soc. Am. 91 (6), June 1992),Felipe Gaitan et al. modeled the motion of acoustically driven bubblesbased on the results of their single bubble experiments. The authors'experimental apparatus included a liquid filled levitation cell in whicha stationary acoustic wave was excited, the stationary wavecounteracting the hydrostatic or buoyancy force, thus stabilizing abubble injected into the cell and allowing it to remain suspended in theliquid indefinitely.

Avik Chakravarty et al., in a paper entitled Stable SonoluminescenceWithin a Water Hammer Tube (Phys Rev E 69 (066317), Jun. 24, 2004),investigated the sonoluminescence effect using a water hammer tuberather than an acoustic resonator, thus allowing bubbles of greater sizeto be studied. The experimental apparatus employed by the authorsincluded a sealed water hammer tube partially filled with the liquidunder investigation. The water hammer tube was mounted vertically to theshaft of a moving coil vibrator. Cavitation was monitored both with amicrophone and a photomultiplier tube. To stabilize the bubbles withinthe water hammer tube and minimize the effects of the tube walls, in oneembodiment the tube was rotated about its axis.

Although a variety of cavitation systems have been designed, typicallythese systems operate at relatively low pressure, utilize acousticdrivers to cavitate extremely small bubbles, and suffer from a varietyof shortcomings due to the inherent instability of the cavitatingbubbles. The present invention overcomes these limitations by providinga system that operates at high pressures and that can be used to formand cavitate very large, stabilized bubbles.

SUMMARY OF THE INVENTION

The present invention provides a method for initiating cavitation withinthe fluid within a cavitation chamber. In the cavitation preparatorysteps, a hydraulically actuated piston is partially withdrawn and thenthe cavitation chamber is isolated. Once the chamber is isolated, thehydraulic piston is further withdrawn in order to form the desiredcavities and then extended to implode the cavities. At least oneimpeller, located within the cavitation chamber, is rotated in order tostabilize the cavities.

In at least one embodiment, an externally mounted motor is magneticallycoupled to the impeller and used to rotate the impeller. Impellerrotation can be continuous throughout piston retraction/extensioncycling; or initiated after completion of the piston retraction step; orterminated prior to initiating final piston retraction; or terminatedprior to initiating piston extension. If impeller rotation is terminatedprior to completing piston retraction, preferably the blades of theimpeller are positioned to minimize interference between the impellerand the piston, for example by maximizing the distance between theimpeller blades and the cavitation piston. Similarly, if impellerrotation is terminated prior to initiating piston extension, preferablythe blades of the impeller are positioned to minimize interferencebetween the impeller and the piston, for example by maximizing thedistance between the impeller blades and the cavitation piston.

In at least one embodiment of the invention, the cavitation fluid isdegassed prior to rotating the cavitation fluid within the cavitationchamber or retracting/extending the cavitation piston. The degassingstep can be performed within the cavitation chamber or within a separatedegassing chamber. If a separate degassing chamber is used, preferablyit is coupled to the cavitation chamber via a circulatory system. Thedegassing step can be performed using a vacuum pump, acoustic driverscoupled to the degassing chamber, or both.

In at least one embodiment of the invention, cross-contamination betweenthe cavitation fluid and the hydraulic fluid is minimized by interposinga coupling sleeve between the hydraulic driver and the cavitationchamber. Preferably the coupling sleeve is evacuated.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view on an exemplary embodiment;

FIG. 2 illustrates the effects of cavitation fluid rotation on aplurality of bubbles contained within a cavitation chamber;

FIG. 3 is an illustration of a two-bladed impeller assembly suitable foruse with a cylindrical cavity;

FIG. 4 is a perspective view of the impeller shown in FIG. 3;

FIG. 5 is a perspective view of the external body portion of acylindrical cavitation chamber for use with the impeller shown in FIGS.3 and 4;

FIG. 6 is a cross-sectional view of the impeller assembly shown in FIGS.3 and 4 and the chamber shown in FIG. 5;

FIG. 7 is a perspective view of a magnetically coupleable impeller;

FIG. 8 is a cross-sectional view of a cavitation chamber utilizing theimpeller shown in FIG. 7;

FIG. 9 is a perspective view of an alternate embodiment of amagnetically coupleable impeller;

FIG. 10 is a cross-sectional view of a cavitation chamber utilizing theimpeller shown in FIG. 9;

FIG. 11 is a cross-sectional view of an alternate cylindrical cavitationchamber utilizing a dual magnetic coupling system;

FIG. 12 is an end view of a ferromagnetic impeller rotor;

FIG. 13 is an end view of a permanent magnet impeller rotor;

FIG. 14 is an end view of the impeller rotor of FIG. 12 embedded withina second material in order to eliminate rotor edges;

FIG. 15 is an end view of the impeller rotor of FIG. 13 embedded withina second material in order to eliminate rotor edges;

FIG. 16 is an end view of a stator;

FIG. 17 is a cross-sectional view of another embodiment of the inventionutilizing an electromagnetic coupling/drive system;

FIG. 18 is a cross-sectional view of an embodiment in which degassing isperformed within the cavitation chamber;

FIG. 19 is a cross-sectional view of an embodiment in which degassing isperformed within a separate degassing chamber;

FIG. 20 is a cross-sectional view of a spherical cavitation chamber foruse with the invention;

FIG. 21 is a cross-sectional view of a mechanically coupleable impellerassembly and the spherical cavitation chamber of FIG. 20; and

FIG. 22 is a cross-sectional view of a magnetically coupleable impellerassembly and the spherical cavitation chamber of FIG. 20.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

System Overview

FIG. 1 is a cross-sectional view of the principal elements of theinvention implemented in an exemplary embodiment. The primary componentof system 100 is the cavitation chamber 101. Although in the illustratedembodiment cavitation chamber 101 is cylindrically-shaped, it will beappreciated that the invention is not so limited and that cavitationchambers of other configurations (e.g., spherical, conical, cubical,rectangular, etc.) can also be used with the present invention. Chamber101 must be fabricated to withstand high operating pressures, preferablypressures of at least 1,000 PSI, more preferably pressures of at least10,000 PSI, and still more preferably pressures of at least 100,000 PSI.Additionally, chamber 101 should be designed to properly seal whenevacuated, thus allowing degassing procedures to be performed in situ.Typically chamber 101 is fabricated from multiple pieces which aresubsequently held together using brazing, a plurality of bolts, or othermeans. It will be appreciated that if chamber 101 is fabricated frommultiple pieces, suitable sealing means (e.g., o-rings, gaskets, etc.)must be used to seal the individual pieces together, thus allowing thechamber to operate at the desired pressures. In the illustratedembodiment, chamber 101 is fabricated from a single block of material102, for example stainless steel, into which a cylindrical hole has beenbored.

Chamber 101 can be fabricated from any of a variety of materialsalthough there are some constraints placed on the chamber material.First, the material is preferably machinable, thus simplifying thefabrication process. Second, the material should be conducive to highpressure operation. Third, if the chamber is to be operated at a hightemperature, the chamber material should have a relatively high meltingtemperature. Additionally, depending upon the process used to assembleindividual chamber pieces together (e.g., brazing), a high meltingtemperature may be desirable as an aid to fabrication and assembly.Fourth, the chamber material should be corrosion resistant, thusallowing the chamber to be used repeatedly and with a variety ofliquids. Fifth, the material should be hard enough to allow a goodsurface finish to be obtained. In one preferred embodiment of theinvention, the chamber is fabricated from 17-4 precipitation hardenedstainless steel.

With respect to the dimensions of the chamber, both inner and outerdimensions, the selected sizes depend upon the intended use of thechamber. For example, smaller chambers are typically preferable forsituations in which it is desirable to limit the amount of cavitatingmedium, for example due to the cost of the medium, or when extremelyhigh peak pressures are desired. On the other hand large chambers, withinside dimensions on the order of 8-10 inches or greater, simplifyexperimental set-up and event observation, and allow for implosion oflarger cavities. Thick chamber walls are preferable, both due to thehigh operating pressures encountered during chamber operation and as ameans of simplifying the coupling of the hydraulic driver to the chamberas described in detail below. In the illustrated embodiment, cylindricalcavitation chamber 101 is 6 inches long with an inside diameter (ID) of3 inches.

As described more fully below, the cavitation medium is degassed priorto the use of the hydraulic driver of the invention. Degassing thecavitation fluid is crucial in order for the collapsing bubbles withinthe cavitation chamber to achieve the desired high velocities, and thushigh temperatures and pressures, at implosion stagnation. The cavitationfluid can be degassed within chamber 101, degassed in a separatedegassing chamber, or degassed in stages such that one stage ofdegassing is performed prior to chamber filling and a second stage ofdegassing is performed within the chamber. Regardless of where thecavitation fluid is degassed, chamber 101 preferably includes a pair ofinlets 103 and 105 thus allowing the chamber to be filled, drained, etc.Preferably inlets 103 and 105 are located at the top and bottomportions, respectively, of chamber 101, and more preferably located atthe uppermost and lowermost portions of chamber 101 as shown, therebyhelping to prevent gas bubbles from being trapped within chamber 101.Inlets 103/105 include valves 107/109, respectively.

As shown in FIG. 1, a hole 111 is bored into the side of chamber 101such that it intersects a lower portion of the cavitation chamber.Although this configuration is preferred, it should be understood thatthe hydraulic driver does not have to be coupled at a specific angle orat a specific location relative to the cavitation chamber in order todrive cavitation within the chamber.

Within hole 111 is cavitation drive piston 113, piston 113 having anoutside diameter (OD) of 0.690 inches in this embodiment. One or moreseals 115 prevent leakage of the cavitation medium around piston 113during the piston stroke. In the preferred embodiment, cavitation drivepiston 113 is coupled to a hydraulically actuated piston 117 via atwo-part piston rod, i.e., rod portions 119 and 121. Preferably rodportions 119 and 121 are threadably coupled together. The two-partpiston rod design simplifies assembly/disassembly as well as systemmaintenance. Furthermore, in terms of research and development devices,this design allows a single hydraulic piston to be easily coupled to anyof a variety of cavitation chambers and cavitation pistons, thusproviding system flexibility at minimal cost. Lastly, this arrangementprovides a simple method of altering the pressure applied by piston 113to the cavitation medium. Specifically, since the peak applied pressureis directly proportional to the effective area of the piston, pressurechanges can be made by altering the ratio of the areas of hydraulicpiston 117 and cavitation drive piston 113.

Due to the need to accommodate piston 113 from full extension to fullretraction, i.e., the piston stroke, either the wall thickness ofchamber housing 102 must be appropriately sized or an additional sleeve(i.e., a spacer) must be added to accommodate the piston stroke. In theillustrated embodiment, with a piston stroke of 3 inches, a couplingsleeve 123 is introduced between housing 102 and hydraulic cylinder 125.In addition to being more economical than sizing chamber housing 102 toaccommodate the entire piston stroke, coupling sleeve 123 providesfurther separation between the hydraulic liquid driving the hydraulicpiston (i.e., piston 117) and the cavitation fluid within chamber 101,thus helping to prevent contamination of either fluid by the other fluiddue to a faulty seal. Preferably coupling sleeve 123 is coupled to avacuum pump 127, thus allowing the sleeve to be evacuated. The inventorhas found that by evacuating sleeve 123 air leakage into chamber 101 isreduced, air leakage leading to a cushioning of the desired cavitationimplosions.

Although not required, in the preferred embodiment coupling sleeve 123is counter-bored into housing 102 and subsequently welded in place.Alternate methods of coupling sleeve 123 to housing 102 include bolts, athreaded hole/collar arrangement, brazing, bonding, etc. In thepreferred embodiment, hydraulic cylinder 125 is held in place via aplurality of bolts 129. Alternately, cylinder 125 can be brazed, bonded,or threadably coupled to sleeve 123. Suitable hydraulic cylinders aremanufactured by Ortman, for example Ortman 3T-NQ with a 2.5 inch bore, 3inch stroke and a 1 inch piston rod.

Hydraulic cylinder 125 is coupled to a valve 131 by hydraulic lines133/135. Although valve 131 can be manually operated, preferably it is asolenoid operated valve(s) (e.g., Continental high flow solenoidoperated valves). Valve 131 applies forward pressure to piston 117through hydraulic lines 133, thus causing piston 117 and coupled piston113 to become extended. Retraction of piston 117 and coupled piston 113is caused by valve 131 applying backward pressure via hydraulic lines135. Although a single hydraulic line 133 and a single hydraulic line135 can be used to extend and retract piston 117, utilizing multiplelines 133/135 allow for more rapid extension/retraction of the pistons.Rapid extension of the pistons is further aided by the use of a nitrogenloaded, bladder type accumulator 137. Valve 131 is also coupled to ahydraulic pump 139 (e.g., Bosch vane type pump) and a reservoir 141. Thecycling of valve 131, and thus hydraulic piston 117 and coupledcavitation piston 113, is controlled by controller 147.

Within chamber 101 is an impeller which, in the illustrated embodiment,is comprised of a pair of impeller blades 143. The impeller is eitherdirectly or indirectly (e.g., magnetically) coupled to a motor, notshown, that rotates the impeller about an axis 145. Indirect couplingoffers the advantage of allowing the entire impeller assembly to becontained within chamber 101, thus making it easier to seal the chamberas the need for drive shaft seals is eliminated.

The impeller of the invention serves many purposes. First, the impellerhelps to keep cavitating bubbles, regardless of their size, away fromthe inner chamber surfaces, thus insuring that the imploding bubbles arecompletely surrounded by liquid. As a result, the implosion symmetry andpeak stagnation temperature and pressure of the imploding bubbles areimproved. Second, the impeller centers the bubble or bubbles along theimpeller's axis. Therefore if the impeller axis is maintained in ahorizontal plane, as preferred, the impeller's rotation can be used toovercome the bubble's tendency to drift upward through the chamber. Thisbenefit is especially important with larger bubbles such as thosepreferably created using the hydraulic driver of the present invention.Third, the impeller can be used to improve the sphericity of the bubblesduring the cavitation process, in particular during the period ofcavitation in which the bubbles are collapsing. As a result, smallerbubble diameters can be achieved prior to bubble deformation ordisintegration.

Once bubbles are formed using the hydraulic piston, as described morefully below, the impeller enclosed with the cavitation chamber can havea variety of effects on the bubbles depending upon the rotationalvelocity of the impeller, the length of time the impeller has beenrotating, cavitation fluid pressure, cavitation fluid composition,density and surface tension. For example, immediately after the impellerstarts to rotate and assuming a relatively low impeller rotationvelocity, bubbles 201 are drawn toward the rotational axis 203. Duringthis stage of rotation and with low rotation velocities, the bubblesremain quasi-spherical in shape as the force exerted by the rotatingfluid is insufficient to overcome the bubbles' tendency to assume aspherical shape, thereby minimizing the bubble's surface tension. As therotational velocity increases, the bubbles 205 are drawn more forcefullytowards the rotational axis 203. Simultaneously, bubbles 205 begin toelongate as illustrated. At this stage typically there is a ‘string’ ofbubbles formed along the rotational axis, the sphericity of each of thebubbles depending strongly on the rotational velocity of the fluid aswell as the size of the individual bubbles. For example bubbles 205, asshown, have begun to elongate while smaller bubbles 207, at the samefluid rotation velocity, remain quasi-spherical in shape. If the bubblesare sufficiently large, or the rotational velocity sufficiently high,often multiple bubbles will coalesce into larger, elongated bubbles 209,the number and size of bubbles 209 depending upon the number of bubbles,their sizes, and the rotational velocity. Whether the bubbles are vaporfilled (evacuated) or gas filled (for example, with gases to bereacted), their behavior is substantially the same.

The impeller can either be rotated continuously or non-continuously. Dueto the force exerted by cavitation piston 113 and the initiallocalization of that force within hole 111, preferably neither impellerblade 143 is located at the intersection of hole 111 and chamber 101during the retraction of piston 113 or during the extension of piston113, thus minimizing interference between the impeller and thecavitation piston. Such interference minimization can be achieved, forexample, by maximizing the distance between all impeller blades 143 andhole 111/cavitation piston 113. By preventing an impeller blade frombeing located near the intersection of hole 111 and chamber 101 duringpiston cycling, potential damage to the impeller blades (e.g., bladebending) can be prevented. In order to accomplish this goal, preferablythe impeller controller (e.g., controller 303 shown in FIG. 3) and thepiston controller (i.e., controller 147) time the rotation of theimpeller and the cycling of piston 113 to insure that the impellerblades are not located near the intersection of hole 111 and chamber 101during piston cycling. Alternately, the impeller blades can be rotatedprior to piston cycling and then stopped at a location other than theintersection of hole 111 and chamber 101 prior to piston cycling. As thecavitation fluid will continue to rotate for a short period of timeafter impeller rotation cessation, some of the beneficial effects of theimpeller are still realized. If desired, impeller rotation can bere-initiated after piston cycling or after the first cycle half (i.e.,piston retraction). Alternately, piston 113 can be retracted, therebycreating one or more bubbles, prior to rotation of the impeller. Theimpeller can then be rotated in order to center and/or stabilize thebubble(s). Then after bubble stabilization, the impeller blades can bestopped, preferably at a location other than the intersection of hole111 and chamber 101, and the piston extended, thereby causing theimplosion of the cavity. Alternately, the impeller assembly can bedesigned to insure that the blades and assembly can withstand operationof the cavitation piston, thus allowing continuous rotation of theimpeller during piston cycling. Design considerations to insure suchoperation include material selection (e.g., titanium), blade thickness,and impeller assembly dimensions (e.g., distance between blades 143 andthe inner wall of chamber 101).

As previously noted, a variety of different bubble geometries can beachieved by varying the impeller rotation velocity, selecting eithercontinuous or non-continuous impeller rotation, and controlling thebubble density and bubble volume. Additionally it will be appreciatedthat other parameters such as impeller design and cavitation fluidcomposition affect the bubble geometry. With respect to composition, thetwo primary attributes of the selected cavitation medium which controlthe response of a bubble to the rotating impeller is the medium'sviscosity and surface tension. Increasing the viscosity of thecavitation medium affects the ease by which the impeller can rotatewithin the fluid as well as the rate at which bubbles can move withinthe fluid, both during impeller rotation and after cessation of impellerrotation. The surface tension affects the extent of bubble elongation inresponse to impeller rotation.

Impeller Design

The invention is not limited to a specific design for the impellerassembly, chamber, or hydraulic driver. For example, the impeller can beeither mechanically coupled or magnetically coupled to the impellermotor. FIG. 3 is an illustration of a two-bladed impeller assembly 300suitable for use with a cylindrical cavity, such as that shown in FIG.1.

Impeller assembly 300 is mechanically coupled to a drive motor 301 whichis attached to controller 303. As previously noted and as shown in FIG.3 and the impeller prospective view of FIG. 4, impeller assembly 300 hasa pair of impeller blades 305. Note that in FIG. 4, impeller assembly300 has been rotated to provide a clearer view of impeller blades 305.For applications in which stable on-axis bubbles are desired, preferablythe outside diameter of impeller assembly 300 is smaller than the insidediameter of the cavitation chamber by a sufficient amount to minimizewall turbulence that can be caused by rotating the impeller blades innear proximity to the cavity wall. For applications in which bubbleclouds are desired, preferably impeller assembly 300 utilizes thickimpeller blades and the outside diameter of the impeller is onlyslightly smaller than the inside of the cavitation chamber, therebymaximizing wall turbulence.

For ease of fabrication, impeller assembly 300 is fabricated from acylinder. In one exemplary embodiment the cylinder is 6 inches long withan outside diameter of 2.5 inches and a wall thickness of 0.0625 inches.Preferably impeller assembly 300 is fabricated from a metal such asstainless steel. During impeller fabrication, most of the wall of thecylinder is machined away, leaving only blades 305 and a portion 307 ofthe cylinder at either end. Cylinder end caps 308 and 309 are attachedto end portions 307 using any of a variety of means, including but notlimited to press-fitting, bonding, brazing or bolting the piecestogether. As shown in further detail below, end cap 309 includes aspindle 311 which confines the axis of rotation of the impeller alongthe centerline of the chamber. End cap 308 includes a drive shaft 313,the drive shaft providing a means for coupling impeller assembly 300 tomotor 301. Although the invention does not require that impeller 300 usetwo blades 305 as shown, the inventor has found that two blades providesufficient fluid rotation capabilities while also providing a strongmechanical design. Other impeller configurations, however, are clearlyenvisioned (e.g., three blades, four blades, etc.). The primaryrequirements placed on the number and locations of the impeller bladesare (i) balanced and stable operation during rotation and (ii)minimization of impeller created turbulence (assuming bubble clouds arenot desired).

FIG. 5 is a perspective view of the external body portion of acylindrical cavitation chamber, such as the one shown in FIG. 1, for usewith impeller assembly 300. To simplify fabrication, the chamber isfabricated from a single piece of material 501, preferably stainlesssteel. A cylindrical hole 502 is bored into block 501 such that impellerassembly 300 fits within the hole as shown in the chamber/impellercross-sectional view of FIG. 6. For the sake of illustration simplicity,FIG. 6 does not include those aspects of the invention corresponding tothe cavitation piston and associated hardware. Assuming an impeller withan outside diameter of 2.5 inches, preferably the inside diameter ofcavitation cavity 600 is 3.0 inches. Although hole 502 need not be boredcompletely through block 501 as shown, the inventor has found thatchamber assembly and maintenance is simplified by doing so. Accordinglythe preferred embodiment of the invention uses a pair of end caps601/603 to seal chamber 600, the end caps preferably bolted to block 501with a plurality of bolts 605 and sealed with one or more sealingmembers 607 (e.g., o-rings). End cap 601 includes one or more bearings609 to insure proper rotation of impeller spindle 311, and thus impeller300. End cap 603 preferably includes at least one bearing 611 andmultiple seals 613. A secondary end cap 615 with sealing members 617(e.g., o-rings) may be used, as shown, to hold seals 613 and bearings611 in place and to provide additional sealing of the chamber.Preferably multiple Teflon o-rings 619 are inset into both end caps601/603 as shown, o-rings 619 helping to seal chamber 600 as well asproviding a low friction surface between the impeller end caps and thechamber end caps.

The sealing members (i.e., seals 607, 613 and 617) are designed toinsure that cavitation chamber 600 can be either evacuated, preferablyto a pressure of less than the vapor pressure of the cavitation fluid,or pressurized, preferably to a pressure of at least 1,000 PSI, morepreferably to a pressure of at least 10,000 PSI, and still morepreferably to a pressure of at least 100,000 PSI. Thus the sealingmembers are designed to allow the chamber to be either evacuated fordegassing or pressurized during operation. It will be appreciated thatthe invention is not limited to a particular seal arrangement and thatthere are numerous means for adequately sealing chamber 600. The exactnature of a particular seal depends on whether the surfaces to be sealedare static, such as end cap 603 and chamber body 501, or dynamic, suchas drive shaft 313 and end cap 603. Depending upon the intendedcavitation medium as well as the desired pressure ranges, a variety ofsealing member types can be used with the invention including, but notlimited to, o-rings, static packing seals such as gaskets and dynamicpacking seals such as flanges, rings, and adjustable soft packings.

As noted with respect to FIG. 1, preferably chamber 600 includes a pairof chamber inlets 103/105, thus allowing the chamber to be filled,drained and/or coupled to a cavitation fluid circulatory system asdescribed further below as well as in co-pending U.S. patent applicationSer. No. 11/001,720, filed Dec. 1, 2004, the entire disclosure of whichis incorporated herein for any and all purposes.

Although the impeller assembly can be mechanically driven as describedin detail relative to FIGS. 3-6, the impeller can also be magneticallycoupled/driven as described more fully below.

FIGS. 7-8 illustrate an embodiment of an impeller assembly suitable foruse with cylindrical chamber 101 of FIG. 1. As in the above figuresdepicting a mechanically coupled impeller assembly, FIGS. 7-8 do notinclude those aspects of the invention directed to the cavitationpiston/driver assembly. Furthermore, the operation and design ofimpeller assembly 700 is similar to impeller assembly 300 except for theinclusion of at least one permanent magnet 701, and preferably aplurality of permanent magnets 701 of alternating magnetic polarity, incylinder end cap 308. Additionally, spindle 313 is shorter in thisembodiment of the impeller assembly as it does not need to be longenough to be mechanically coupled to an external motor.

FIG. 8 is a cross-sectional view of impeller 700 within chamber 800. Inthe illustrated embodiment, chamber 800 is comprised of two sections,801 and 802, bolted together with a plurality of bolts 803. One or moresealing members 805 (e.g., o-rings) provide the desired seal betweensections 801 and 802. Sealing members 805 are designed to insure thatcavitation chamber 800 can be either evacuated, preferably to a pressureof less than the vapor pressure of the cavitation fluid, or pressurized,preferably to a pressure of at least 1,000 PSI, more preferably to apressure of at least 10,000 PSI, and still more preferably to a pressureof at least 100,000 PSI. Thus the sealing members are designed to allowthe chamber to be either evacuated for degassing or pressurized duringoperation. It will be appreciated that the invention is not limited to aparticular seal arrangement and that there are numerous means foradequately sealing chamber 800.

A cylindrical hole 807 is bored into sections 801 and 802 such thatimpeller 700 fits within the hole as shown in the chambercross-sectional view of FIG. 8. Spindles 311 and 313, and thus impeller700, are centered within hole 807 using bearings 809 and 810,respectively. In addition to centering impeller 700, bearings 809 and810 insure the free rotation of the impeller. In one embodiment,bearings 809 and 810 are fabricated from a material with a lowcoefficient of friction, such as Teflon. To insure that end caps 308 and309 of impeller 700 do not rub against sections 801 and 802 of chamber800, preferably one or more spacers 811 are interposed between the endcaps and the chamber internal surfaces as shown. In one embodiment,spacers 811 are comprised of Teflon o-rings. It will be appreciated thatalthough bearings 809/810 and spacers 811 are preferably comprised ofTeflon, alternate materials may be required depending upon thecomposition, temperature and corrosive characteristics of the cavitationmedium.

In the illustrated embodiment, the outer surface of end portion 813 ofchamber section 801 is cylindrically shaped. A cup-shaped member 815 isconfigured to rotate about end portion 813. Optionally one or morespacers 817, for example Teflon spacers, are used to insure the smoothrotation of member 815. Embedded within an internal surface of member815 adjacent to the external surface of end cap 308 is a plurality ofpermanent magnets 819 of alternating magnetic polarity. A drive shaft821 of member 815 is coupled to a drive motor and associated controller(e.g., drive motor 301 and controller 303), not shown. Due to themagnetic field generated by magnets 819 and its interaction with themagnetic field generated by magnets 701, rotation of member 815 causesthe rotation of impeller 700 within chamber 800. Similarly, impeller 700can be positioned within chamber 800 by controlling the rotationalposition of member 815.

As noted with respect to FIGS. 1 and 6, preferably the embodiment ofchamber 800 shown in FIG. 8 also includes a pair of chamber inlets103/105.

In addition to the previously cited selection criteria for the chambermaterial, this embodiment of the invention requires that the materialshould be relatively transparent to the magnetic fields generated bymagnets 701 and 819, thus insuring that the rotation of member 815results in the rotation of impeller 700.

The embodiment shown in FIGS. 7-8 is only meant to illustrate onepreferred method of magnetically coupling to the impeller of theinvention. It will be appreciated that there are many methods which canbe used to magnetically rotate the chamber's internal impeller. Forexample, FIGS. 9 and 10 illustrate an alternate embodiment in whichpermanent magnets 901 are embedded in the end surface of end cap 308 asshown. As a consequence of the location of magnets 901, the overallshape of chamber 1000 is different from that of the previous embodimentwith chamber 1000 being comprised of sections 1001 and 1002. Although avariety of means can be used to couple the chamber sections together, asin the previous embodiment preferably the two sections are boltedtogether with a plurality of bolts 1003 and sealed with one or moresealing members 1004. Impeller 900 is held in place within chamber 1000,while still being free to rotate, using bearings and/or spacers1005-1007.

As illustrated, the shape of the end portion of chamber section 1001 issuch that the chamber wall adjacent to impeller magnets 901 is thinenough to allow an external magnetic field to interact with the magneticfield produced by magnets 901 while still being thick enough to handlepeak pressures. A cup-shaped member 1009 is configured to rotate aboutthe end portion of section 1001. Optionally one or more spacers 1011,for example Teflon spacers, are used to properly space and allow therotation of member 1009. Embedded within member 1009 is a plurality ofpermanent magnets 1013 of alternating magnetic polarity, two suchmagnets being shown in the cross-sectional view of FIG. 10. A driveshaft 1015 provides a means of coupling member 1009 to a drive motor andassociated controller (e.g., drive motor 301 and controller 303), notshown. Due to the magnetic field generated by magnets 1013 and itsinteraction with the magnetic field generated by magnets 901, rotationof member 1009 causes the rotation of impeller 900 within chamber 1000.

FIG. 11 is a cross-sectional view of an alternate embodiment configuredto provide additional torque over the impeller. As shown, thisembodiment combines magnetic coupling features of the previous twoembodiments. In particular, chamber section 1101 is shaped to allowclose proximity of cup-shaped member 1103 in two planes, thus allowingembedded magnets 1105 to interact with impeller magnets 1106 in oneplane and embedded magnets 1107 in a second plane. As in the previousembodiments, a plurality of spacers 1109 insure proper spacing of member1103 relative to chamber section 1101 while still permitting its freerotation. This embodiment allows a stronger magnetic field to begenerated by magnetic coupler 1103 on the impeller. A drive shaft 1111allows member 1103 to be coupled to a drive motor/controller (notshown).

It will be appreciated that the magnetic coupling systems illustrated inFIGS. 7-11 or those illustrated below can be duplicated on the oppositeend of the impeller, thereby easily doubling the strength of the drivemechanism by providing magnetic coupling and impeller rotation on bothimpeller ends.

In addition to using any of a variety of magnetic coupling systems basedon permanent magnets, it will be appreciated that the inventor alsoenvisions countless variations utilizing electromagnetic coupling means.In such a system, the impeller assembly includes a rotor at one end ofthe impeller assembly, or rotors at both ends of the impeller assembly,the rotor(s) including either permanent magnets or material susceptibleto a magnetic field (e.g., a ferromagnetic material). An electromagneticstator, external to the chamber and surrounding the rotor(s), providesthe force required to turn the rotor(s) and thus the impeller assembly.

FIGS. 12 and 13 provide end views of the rotors of exemplary impellerassemblies, rotor 1201 utilizing a ferromagnetic rotor and rotor 1301utilizing a permanent magnet rotor. As shown, rotor 1201 includes 8teeth 1203 while rotor 1301 includes 2 teeth 1303. It should beunderstood that the invention is not limited to specific rotor designs,rather rotors 1201 and 1301 are merely illustrative of the invention. Inpreferred embodiments of the invention, the rotors are embedded within asecond material, thus eliminating the edges of the teeth. FIGS. 14 and15 provide end views of two such embedded rotors. FIG. 14 shows a rotorassembly 1400 in which an 8 tooth ferromagnetic rotor 1401 (shown inphantom) is embedded within a non-ferromagnetic material 1403 (e.g., aceramic). Similarly, FIG. 15 shows a rotor assembly 1500 in which a 2tooth permanent magnet rotor 1501 (shown in phantom) is embedded withina non-ferromagnetic material 1503. By embedding the rotors within acylindrically shaped second material, the rotor does not cause unwantedturbulence within the cavitation medium. Although the present inventionis not limited to specific stator designs, an exemplary stator 1600 isshown in FIG. 16, stator 1600 having 12 stator poles divided into threestator pole sets 1601-1603.

FIG. 17 is a cross-sectional view of a chamber 1700 which is similar tothe configuration shown in FIG. 8. However the impeller assembly ofchamber 1700 is driven with an electromagnetic assembly in which a rotor1400 (shown in phantom) is embedded within impeller end-cap 308. Asshown, the electromagnetic assembly includes a stator 1600 coupled to amotor driver 1701 and a controller 1703. It will be appreciated thatthis is simply one possible configuration of the invention utilizing anelectromagnetic system for driving the impeller assembly.

The embodiments shown in FIGS. 3-17 are only meant to illustrate some ofthe various methods of mechanically, magnetically or electromagneticallycoupling to and driving the impeller assembly of the invention. It willbe appreciated that the invention is not limited to a particularimpeller design/shape, chamber design/shape, impeller sealing means,impeller driving means, etc. Nor does the invention require that theshape of the impeller assembly match that of the cavitation chamber.Thus, for example, a cylindrical impeller can be used with a sphericalor rectangular chamber.

Degassing System

As previously noted, degassing of the cavitation fluid can be performedwithin the cavitation chamber, within a separate degassing chamber, ordegassed in stages such that the initial stages of degassing areperformed prior to chamber filling and the final stages of degassing areperformed within the cavitation chamber. FIG. 18 illustrates oneembodiment of the invention in which degassing is performed within thecavitation chamber itself. FIG. 18, as well as FIG. 19 which follows,are based on the cavitation system shown in FIG. 1 although it will beunderstood that these degassing systems are not limited to the specificdesigns for the chamber, impeller assembly and/or hydraulic driver shownin FIG. 1. Additionally, for the sake of illustration simplicity, FIGS.18-19 do not include all aspects of the driver and/or impellerassemblies as these aspects are described in detail elsewhere withinthis specification.

The first step in degassing the cavitation fluid within the chamber isto fill the chamber. The chamber can be filled via inlet 103, forexample by first evacuating chamber 101, thus allowing the cavitationfluid to easily flow into the chamber. If chamber 101 is not firstevacuated, the air exiting the chamber must either be allowed to passthrough the entering fluid, or pass out through a separate inletpositioned near or at the uppermost portion of the chamber (not shown).Alternately the cavitation fluid can be pumped up through inlet 105,thus allowing the exiting air to pass out of inlet 103. Once filled, thecavitation fluid is degassed by vacuum pump 1801. Preferably pump 1801is attached to chamber 101 via a three-way valve, e.g., valve 107, thusallowing the chamber to either be coupled to pump 1801 or open to theatmosphere via conduit 1803. Although pump 1801 can degas the cavitationfluid within chamber 101 to a sufficient degree for many applications,preferably additional degassing stages are implemented. A detaileddescription of the additional degassing stages are provided below. Ingeneral, the additional degassing requires that the cavitation fluid becavitated, thus further reducing the concentration of air/vapor withinthe fluid. Although hydraulically actuated cavitation piston 113 can beused for this purpose, in at least one embodiment of the invention oneor more acoustic drivers 1805 are coupled to chamber 101, drivers 1805providing a convenient means of cavitating and degassing the fluid asdescribed more frilly below.

FIG. 19 illustrates an alternate degassing system. As shown, thehydraulically driven cavitation chamber 101 is coupled via lines 1901and 1903 to a degassing chamber 1905. Preferably degassing chamber 1905serves a dual purpose; both as a degassing chamber and a fluidreservoir. Chamber 1905 is coupled to a vacuum pump 1907 via a three-wayvalve 1909, valve 1909 allowing chamber 1905 to be coupled to pump 1907(e.g., for degassing purposes) or open to the atmosphere via conduit1911. Pump 1913 is used to pump the cavitation fluid from degassingchamber/reservoir 1905 into cavitation chamber 101.

In one approach, all cavitation fluid degassing is performed withinchamber 1905. Once degassed, chamber 101 is filled with the cavitationfluid, preferably by simply pumping the fluid through line 1903 withpump 1913 into evacuated chamber 101. After it is filled, chamber 101can be decoupled from the degassing system, for example with valves107/109. In an alternate approach, the cavitation fluid can be degassedfirst within chamber 1905, and then degassed further within cavitationchamber 101. Preferably chamber 101 is decoupled from degassing chamber1905 prior to performing further degassing within chamber 101. In yetanother alternate approach, after the initial degassing procedure hasbeen completed and cavitation chamber 101 is operable, the cavitationfluid is periodically pumped through the system and degassed withinchamber 1905. One benefit of this approach is the removal of gases thathave been generated as a by-product of reactions taking place withinchamber 101.

Although degassing with vacuum pump 1907 attached to chamber/reservoir1905 is sufficient for many applications, as previously noted relativeto the system shown in FIG. 18, further degassing via cavitation ispreferred. In one preferred embodiment cavitation degassing is performedwithin chamber 1905 by attaching one or more drivers 1915 (e.g.,acoustic drivers) to chamber 1905 as shown. In an alternate preferredembodiment, after completion of the initial stage of degassing withinchamber 1905, cavitation degassing is performed within chamber 101,either using the hydraulically actuated cavitation piston 113 oradditional drivers (e.g., acoustic drivers) attached to chamber 101, forexample as shown in FIG. 18 (i.e., drivers 1805).

If the cavitation fluid is degassed in a separate chamber and thenpumped into the cavitation chamber as in the embodiment illustrated inFIG. 19, preferably the system also includes a bubble trap 1917 thatimmediately follows the outlet of pump 1913 as shown, thus helping toeliminate any bubbles generated by the pump itself. Preferably bubbletrap 1917 is coupled to chamber 1905 via valve 1919 and conduit 1921.During use, bubbles that are trapped float to the top portion of trap1917 where they are periodically removed via valve 1919 and conduit1921, conduit 1921 being indirectly coupled to vacuum pump 1907. Onesuitable configuration for bubble trap 1917 is shown in co-pending U.S.patent application Ser. No. 11/002,448, filed Dec. 1, 2004, the entiredisclosure of which is incorporated herein for any and all purposes.

If a separate degassing chamber and/or circulatory system is used,preferably a filter 1923 is included, the filter preceding the chamberinlet port into which the cavitation fluid is pumped (e.g., inlet 105).Filter 1923 is used to remove contaminants from the cavitation fluidthat could potentially disrupt the cavitation process. The contaminantsmay be native to the cavitation fluid. Alternately, or in addition tonative contaminants, the contaminants to be removed may be a product ofthe cavitation process itself, for example resulting from the flow ofthe cavitation fluid through a heat exchange system or from the effectsof the cavitation process on the internal surfaces of the cavitationchamber. Alternately, or in addition to the above-describedcontaminants, the contaminants may be a by-product of a reaction takingplace within the cavitation chamber. It will be appreciated that theexact nature of filter 1923 depends upon the type of cavitation fluid aswell as the type and size of contamination, i.e., impurity, to beremoved from the cavitation fluid. As filters are well know, furtherdescription is not provided herein.

In at least one of the preferred embodiments in which an externaldegassing and/or circulatory system is used, a heat exchange system 1925is coupled to the system, thus allowing the temperature of thecavitation fluid to be controlled. The cavitation fluid can becontinually pumped through heat exchange system 1925 during chamberoperation, or used to alter the temperature of the fluid prior tochamber operation, or used to periodically alter the temperature of thefluid. Furthermore heat exchange system 1925 can be used to cool thecavitation fluid below ambient temperature, to cool the cavitation fluidby removing excess heat from the cavitation chamber, or to heat thecavitation fluid to a desired temperature.

In a preferred embodiment heat exchange system 1925 is used to cool thecavitation fluid below ambient temperature, thus lowering the vaporpressure of the fluid and allowing higher velocities to be achieved bythe collapsing bubbles within chamber 101. As a result, the cavitatingbubbles generate higher temperatures at collapse stagnation. Although inthis embodiment heat exchange system 1925 is typically located afterpump 1913 and as close to cavitation chamber 101 as reasonable, thusminimizing the introduction of heat into the cooled cavitation mediumfrom pump 1913, the surroundings, etc., it will be appreciated that thelocation of system 1925 relative to pump 1913 depends on the ambienttemperature, the temperature to which the cavitation fluid is to bemaintained, and the preferred operating temperature of the pump.

In another embodiment heat exchange system 1925 cools the cavitationfluid by withdrawing excess heat generated within the chamber. Theexcess heat can be a product of the cavitation process itself as thecavitating bubbles generate heat within the fluid, for example due toviscous effects. The excess heat can also be the product of reactionstaking place within the chamber which are promoted by the cavitationprocess. Such reactions include both chemical reactions and nuclearreactions. The excess heat can also be the result of heat conducted intothe cavitation medium from cavitation piston 113. In embodiments inwhich the cavitation fluid is a hot liquid such as a molten metal orsalt, heat exchange system 1925 is preferably located before pump 1913rather than after pump 1913 as shown in FIG. 19. Such a mountinglocation is preferred as it cools the cavitation fluid beforeintroducing it into pump 1913, thus minimizing the pump operatingtemperature for such applications. It will be appreciated that whetherheat exchange system 1925 is located before or after pump 1913 dependsupon the temperatures of the cavitation fluid before and after heatexchange system 1925, the ambient temperature and the preferredoperating temperatures of pump 1913 and the cavitation fluid.

In another embodiment heat exchange system 1925 is used to heat thecavitation fluid to the desired operational temperature. Such heating isuseful, for example, to promote specific reactions (e.g., chemicalreactions) within the cavitation fluid or to maintain the cavitatingmedium in the fluid phase (i.e., heating to above the meltingtemperature of the medium). Preferably heat exchange system 1925 ispositioned relative to pump 1913 as shown, thus allowing pump 1913 topump a relatively cool fluid. As previously noted, the location of heatexchange system 1925 relative to pump 1913 depends upon the temperaturesof the cavitation fluid before and after heat exchange system 1925,ambient temperature and the preferred operating temperatures of pump1913 and the cavitation fluid.

Detailed descriptions of the implementation of a heat exchange system1925 with a cavitation fluid circulatory system are provided inco-pending U.S. patent application Ser. No. 10/961,353, filed Oct. 7,2004, the entire disclosure of which is incorporated herein for any andall purposes. With respect to the actual heat exchange system, suchsystems are well known by those of skill in the art and thereforedetailed descriptions are not provided herein.

If sufficient heat is withdrawn from the cavitating liquid by heatexchange system 1925, the excess heat can be used to drive any of avariety of thermally powered systems such as heaters, thermoelectricgenerators and steam turbines (not shown), thus producing electricitythat can be used for a variety of applications, including reduction ofthe electrical demands of the cavitation system itself.

If a separate degassing chamber is used and coupled to the primarycavitation chamber via a circulatory system as shown in FIG. 19,preferably the circulatory system provides a simple means of eithercirculating the fluid or draining the cavitation chamber (i.e., chamber101). A benefit of such a system is that it allows chamber 101 to bedrained without draining the circulatory system, thus minimizingcavitation fluid loss, exposure to the atmosphere and possiblecontamination. Methods of implementing a circulatory system withcavitation chamber 101 are provided in co-pending U.S. patentapplication Ser. No. 11/001,720, filed Dec. 1, 2004, the entiredisclosure of which is incorporated herein for any and all purposes.

Cavitation Fluid Preparation

In order to achieve high intensity cavity implosions, the cavitationmedium must first be degassed. It should be understood that the presentinvention is not limited to a particular degassing technique, and thetechniques described herein are for illustrative purposes only.

The first step in the degassing method is to fill the degassing chamberwith cavitation fluid. As previously described, the degassing chambercan either be the actual cavitation chamber 101 or a separate degassingchamber (e.g., chamber 1905) which is either coupled or non-coupled tocavitation chamber 101. Once the chamber is filled, the cavitation fluidis degassed with a vacuum pump (e.g., pump 1805 with the cavitationchamber or pump 1907 with separate degassing chamber 1905). The amountof time required during this step depends on the volume of cavitationfluid to be degassed and the capabilities of the vacuum system.Preferably the vacuum pump evacuates the chamber in which the cavitationfluid resides until the pressure within the chamber is close to thevapor pressure of the cavitation fluid, for example to a pressure ofwithin 0.2 psi of the vapor pressure of the cavitation fluid or morepreferably to a pressure of within 0.02 psi of the vapor pressure of thecavitation fluid. Typically this step of the degassing procedure isperformed for at least 1 hour, preferably for at least 2 hours, morepreferably for at least 4 hours, and still more preferably until thereservoir pressure is as close to the vapor pressure of the cavitationfluid as previously noted.

Once the fluid within the chamber is sufficiently degassed using thevacuum pump, preferably further degassing is performed by cavitating thefluid, the cavitation process tearing vacuum cavities within thecavitation fluid. As the newly formed cavities expand, gas from thefluid that remains after the initial degassing step enters into thecavities. During cavity collapse, however, not all of the gas re-entersthe fluid. Accordingly a result of the cavitation process is the removalof dissolved gas from the cavitation fluid via rectified diffusion andthe generation of bubbles.

As previously described, cavitation as a means of degassing the fluidcan be performed within cavitation chamber 101 or separate degassingchamber 1905. Furthermore, any of a variety of techniques can be used tocavitate the fluid. Although cavitation piston 113 can be used duringdegassing, in the preferred embodiment of the invention one or moreacoustic drivers (e.g., drivers 1805 or 1915) are coupled to thedegassing chamber. Acoustic drivers can be fabricated and mounted, forexample, in accordance with co-pending U.S. patent application Ser. No.10/931,918, filed Sep. 1, 2004, the entire disclosure of which isincorporated herein for any and all purposes. Assuming acoustic driversare used, the operating frequency of the drivers depends on a variety offactors such as the sound speed of the liquid within the chamber, theshape/geometry of the chamber, the sound field geometry of the drivers,etc. In at least one embodiment the operating frequency is within therange of 1 kHz to 10 MHz. The selected frequency can be the resonantfrequency of the chamber, an integer multiple of the resonant frequency,a non-integer multiple of the resonant frequency, or periodicallyaltered during operation.

For high vapor pressure liquids, preferably prior to theabove-identified cavitation step the use of the vacuum pump (e.g., pump1801 or pump 1907) is temporarily discontinued. Next the fluid withinthe chamber (e.g., chamber 101 or chamber 1905) is cavitated for aperiod of time, typically for at least 5 minutes and preferably for morethan 30 minutes. The bubbles created during this step float to the topof chamber due to their buoyancy. The gas removed from the fluid duringthis step is periodically removed from the system, as desired, forexample using vacuum pump 1801 if the chamber used for this degassingstep is chamber 101, or using vacuum pump 1907 if the chamber used forthis degassing step is chamber 1905. Typically the vacuum pump is onlyused after there has been a noticeable increase in pressure within thedegassing chamber, preferably an increase of at least 0.2 psi over thevapor pressure of the cavitation fluid, alternately an increase of atleast 0.02 psi over the vapor pressure of the cavitation fluid, oralternately an increase of a couple of percent of the vapor pressure. Ifacoustic drivers are used, preferably the use of cavitation as a meansof degassing the cavitation fluid is continued until the amount ofdissolved gas within the cavitation fluid is so low that the fluid willno longer cavitate at the same cavitation driver power. If a hydraulicpiston driver(s) is used, preferably either the cavitation/degassingsteps are performed for a predetermined period of time (e.g., at least12 hours, preferably for at least 24 hours, more preferably for at least36 hours, etc.) or until the pressure within the chamber remains stableat the vapor pressure of the cavitation fluid for a predetermined periodof time (e.g., at least 10 minutes, greater than 30 minutes, preferablygreater than an hour, etc.).

The above degassing procedure is sufficient for most applications,however in an alternate embodiment of the invention another stage ofdegassing is performed prior to cavitating the fluid using the hydraulicactuated driver. The first step of this additional degassing stage is toform cavities within the cavitation fluid contained in the degassingchamber. These cavities can be formed using any of a variety of means,including neutron bombardment, focusing a laser beam into the cavitationfluid to vaporize small amounts of fluid, by locally heating smallregions with a hot wire, or by other means. Once one or more cavitiesare formed within the cavitation fluid, acoustic drivers 1805 or 1915,or cavitation piston 113, cause the cavitation of the newly formedcavities, resulting in the removal of additional dissolved gas withinthe fluid and the formation of bubbles. The bubbles, due to theirbuoyancy, drift to the top of the chamber where the gas can be removed,when desired, using a vacuum pump (e.g., pump 1801 or pump 1907). Thisstage of degassing can continue for either a preset time period (e.g.,greater than 6 hours and preferably greater than 12 hours), or until theamount of dissolved gas being removed is negligible as evidenced by thepressure within the chamber remaining stable at the vapor pressure ofthe cavitation fluid for a preset time period (e.g., greater than 10minutes, or greater than 30 minutes, or greater than 1 hour, etc.).

Hydraulic Driver Methodology

In a preferred approach, prior to cavitation and after the cavitationfluid has been degassed as previously noted, and after the cavitationchamber 101 has been filled with the degassed cavitation fluid (assumingthat degassing was performed in a separate degassing chamber), hydraulicpiston 117 and coupled cavitation piston 113 are partially withdrawnfrom the completely extended position. The amount of piston withdrawaldepends, in part, on the compressibility of the cavitation medium. Forexample, a cavitation fluid comprised of a very non-compressible liquid(e.g., a liquid metal such as mercury) typically requires much lesspre-cavitation piston withdrawal than a more compressible liquid (e.g.,acetone). For a compressible liquid such as acetone, a pre-cavitationpiston withdrawal of approximately 25 percent is preferred. During thisstep the chamber can be left open to the degassing and/or circulatorysystem, thus allowing it to automatically fill during piston partialwithdrawal. Alternately, the chamber can be filled-up after completionof the step of partially withdrawing the piston, thus compensating forthe fluid withdrawn during piston withdrawal.

The next step is to isolate the cavitation chamber from any degassingsystems and/or a cavitation fluid circulatory systems to which it iscoupled, for example using valves 107/109. Chamber isolation prior tooperation is required to insure that the desired operating pressures canbe reached.

After chamber isolation, hydraulic piston 117 and coupled cavitationpiston 113 are withdrawn, causing a cavity (e.g., a bubble) to be formedwithin the degassed cavitation fluid. The hydraulic piston 117 andcoupled cavitation piston 113 are then rapidly extended to the fullestpossible extent as limited either by mechanical piston stops or by theresultant back pressure. During piston extension, the previously createdcavity or cavities are compressed, causing cavity implosion. Subsequentcavitation cycles only require cycling cavitation piston 113, i.e., itis unnecessary to open the chamber, partially withdraw the piston,isolate the chamber and cycle the piston. Although the system can beused for single cavitation cycles, preferably multiple cycles areperformed, thus generating high chamber pressures and extremelyenergetic implosions. The maximum cycle rate depends on the speed of thesolenoid valves, the compressibility of the cavitation fluid, thepressure applied by the cavitation piston, the size of the chamber, thenumber of hydraulic lines coupling valves 131 to cylinder 125 and thesize and pressure of accumulator 137. In the preferred embodiment,pistons 117/113 are fully extended at a rate of approximately 0.1seconds per stroke. The system can be cycled, i.e., piston retracted andthen extended, at a rate of up to 20 cycles per second.

In an alternate preferred approach, prior to cavitation and after thecavitation fluid has been degassed and the cavitation chamber 101 filled(assuming the use of a separate degassing chamber), hydraulic piston 117and coupled cavitation piston 113 are completely withdrawn. During thisstep the cavitation chamber can either be open to, or isolated from, anycoupled degassing and/or cavitation fluid circulatory systems. Afterpistons 117/113 are completely withdrawn, the cavitation chamber inlets(e.g., inlets 103/105 controlled via valves 107/109) are opened ifpreviously closed, or left open if previously open.

The next step is to isolate the cavitation chamber from any coupleddegassing and/or cavitation fluid circulatory systems, for example byclosing any inlet valves (e.g., valves 107/109). Once the chamber isisolated, hydraulic piston 117 and coupled cavitation piston 113 areextended to the fullest extent possible as limited either by mechanicalpiston stops or by the resultant back pressure. As a result of theextension of pistons 117/113, the cavitation fluid is compressed and theinternal pressure of the cavitation chamber is increased.

It will be appreciated that the amount that pistons 117/113 can beextended depends, in part, on both the compressibility of the cavitationfluid and the ratio of the areas of pistons 117 and 113. Thus, forexample, if the fluid is extremely uncompressible, such as mercury oranother liquid metal, during this step the pistons would not be able tobe extended very far prior to the back pressure stopping further pistontravel. In such situations the chamber can be opened slightly during theinitial fluid compression step, thus allowing the pistons to travelfurther than would otherwise be allowed. If this approach is taken, thechamber is closed (i.e., isolated) prior to the pistons becoming fullyextended (for example, after the pistons have traveled between 75 and 90percent of their full range).

After chamber isolation and cavitation fluid compression, the cavitationchamber is partially opened, for example to the degassing system and/orcavitation fluid circulatory system to which it is coupled. Preferablythis step is performed by opening a valve located near the top ofcavitation chamber 101, and more preferably at the uppermost portion ofthe cavitation chamber (e.g., valve 107). The valve is only opened by asmall degree and for a short period of time; just sufficient to allowthe internal cavitation chamber pressure to drop to a predeterminedlevel or to change by a predetermined amount. The amount that thepressure is allowed to change governs the size of the cavity that willbe cavitated during the cavitation process, i.e., greater pressurechanges result in larger cavities. It will be appreciated that theinvention does not require a specific cavity size, rather the size to becavitated is dictated by the type of desired reaction and thus theintended reactants and the desired temperature and pressure. Otherfactors which determine the desired pressure change include cavitationfluid compressibility, cavitation chamber size, hydraulic drivercapabilities, cavitation piston effective area, and the degree to whichthe cavitation fluid has been degassed during the prior degassing steps.

Once the pressure has been allowed to change by the predeterminedamount, the cavitation chamber is once again isolated, for example fromany degassing and/or cavitation fluid circulatory systems if such areemployed. After chamber isolation, hydraulic piston 117 and coupledcavitation piston 113 are withdrawn, causing a cavity (e.g., a bubble)to be formed within the degassed cavitation fluid. The hydraulic piston117 and coupled cavitation piston 113 are then rapidly extended to thefullest possible extent as limited either by mechanical piston stops orby the resultant back pressure. During piston extension, the previouslycreated cavity or cavities are compressed, causing cavity implosion.Subsequent cavitation cycles only require cycling cavitation piston 113,i.e., it is unnecessary to open/close the cavitation chamber and adjustthe internal chamber pressure. As in the previous method, the system canbe used either for single cavitation cycles or multiple cavitationcycles, the maximum cycle rate depending on the speed of the solenoidvalves, the compressibility of the cavitation fluid, the pressureapplied by the cavitation piston, the size of the chamber, the number ofhydraulic lines coupling valves 131 to cylinder 125 and the size ofaccumulator 137.

Alternate Configurations

As previously noted, the invention is not limited to cylindricalcavitation chambers such as the one shown in FIG. 1. For example, FIGS.20-22 illustrate an embodiment of the invention utilizing a sphericalcavitation chamber 2001, FIG. 20 showing a cross-sectional view of achamber 2001 and a pair of impeller blades 2003. The degassing aspectsas well as the hydraulic cavitation driver are the same as previouslydescribed relative to chamber 101. Spherical chamber 2001 can befabricated as described in co-pending U.S. patent application Ser. No.10/925,070, filed Aug. 23, 2004, the entire disclosure of which isincorporated herein for any and all purposes. Alternately, sphericalchamber 2001 can be fabricated from multiple portions bolted together,or otherwise joined, and sealed with one or more seals (e.g., o-rings,gaskets, etc.) as shown in FIGS. 21 and 22. Operation of chamber 2001 isthe same as described relative to chamber 101.

FIG. 21 is a cross-sectional view of chamber 2001 fabricated fromchamber portions 2101 and 2102. For the sake of illustration simplicity,neither FIG. 21 nor FIG. 22 include those aspects of the invention thatcorrespond to the cavitation piston and associated hydraulic driversystem. Nor do FIGS. 21 and 22 include any degassing and/or circulatorysystem hardware (e.g., inlets, valves, vacuum pumps, etc.). In thisembodiment, chamber portions 2101/2102 are bolted together with aplurality of bolts 2103 to form the chamber. At least one sealing member2104 (e.g., o-ring, gasket, etc.) seals portion 2101 to portion 2102.Prior to assembling portions 2101/2102, impeller 2105 (which includesimpeller blades 2003) is located within the spherical cavity of chamber2001 such that spindle 2107 is fitted within bearing 2109. Spindle driveshaft 2111 is fitted through a seal/bearing housing 2113 incorporatedwithin chamber portion 2102. Preferably an end cap 2115 is bolted tochamber portion 2102, end cap 2115 including an additional sealingmember 2117. As previously noted, preferably the chamber includes a pairof chamber inlets (not shown), thus allowing the chamber to be filled,drained and/or coupled to a cavitation fluid circulatory and/ordegassing system. As previously noted, impeller 2105 preferably includesat least 2 blades 2003. In use, drive shaft 2111 is coupled to a motor(e.g., motor 301) and a controller (e.g., controller 303) as previouslydescribed relative to the mechanically coupled cylindrical impellershown in FIGS. 3, 4 and 6.

FIG. 22 is a cross-sectional view of an embodiment of the invention usedwith spherical chamber 2001 and magnetically coupled to the impellerdrive system. In this embodiment, as in the mechanically coupledimpeller embodiment shown in FIG. 21, the cavitation chamber iscomprised of two sections 2201 and 2203. Although a variety of means canbe used to join together and seal chamber sections 2201 and 2203, thepreferred approach is with a plurality of bolts 2205 and one or moresealing members 2207 (e.g., o-ring, gasket, etc.). Prior to assemblingportions 2201 and 2203, impeller 2209 is located within the sphericalcavity of chamber 2001 such that spindle 2211 is fitted within bearing2213 and spindle 2215 is fitted within bearing 2217. In one embodiment,bearings 2213 and 2217 are fabricated from a material with a lowcoefficient of friction, such as Teflon.

In the illustrated embodiment, embedded within cylindrically-shaped endportion 2219 of impeller 2209 is a plurality of permanent magnets 2221of alternating magnetic polarity. The outer surface of end portion 2223of chamber section 2203 is cylindrically shaped and is configured suchthat the chamber wall adjacent to the section of portion 2219 containingthe embedded magnets 2221 is relatively thin. A cup-shaped member 2225is configured to rotate about end portion 2223. Preferably one or morespacers 2227, for example Teflon spacers, are used to insure the smoothrotation of member 2225. Embedded within an internal surface of member2225 adjacent to magnets 2221, is a plurality of permanent magnets 2229of alternating magnetic polarity. A drive shaft 2231 of member 2225 iscoupled to a drive motor and controller (not shown). Due to the magneticfield generated by magnets 2229 and its interaction with the magneticfield generated by magnets 2221, rotation of member 2225 causes therotation of impeller 2209 within chamber 2001. As previously noted,preferably the chamber includes a pair of chamber inlets (not shown),thus allowing the chamber to be filled, drained and/or coupled to acavitation fluid circulatory system. Preferably impeller 2009 uses atleast two blades 2003.

It will be appreciated that any of the previously described magneticcoupling/drive systems can also be used with either a spherical chambersuch as that shown in FIG. 20, or with other shaped cavitation chambers.Such magnetic coupling/drive systems can utilize permanent magnets,electromagnets or a combination of the two.

As will be understood by those familiar with the art, the presentinvention may be embodied in other specific forms without departing fromthe spirit or essential characteristics thereof. Accordingly, thedisclosures and descriptions herein are intended to be illustrative, butnot limiting, of the scope of the invention which is set forth in thefollowing claims.

1. A method of initiating cavitation within a cavitation fluid within acavitation chamber, the method comprising the steps of: retracting acavitation piston coupled to a hydraulic driver and coupled to thecavitation chamber, wherein said cavitation piston is retracted from afully extended position to a first partially withdrawn position;isolating the cavitation chamber; magnetically coupling an impellerassembly within the cavitation chamber to an impeller drive system, saidimpeller drive system external to the cavitation chamber; rotating atleast one impeller corresponding to said impeller assembly with saidimpeller drive system, wherein cavitation fluid within the cavitationchamber rotates in response to said impeller rotating step; retractingsaid cavitation piston from said first partially withdrawn position to asecond withdrawn position, wherein said second withdrawn position isfurther withdrawn than said first partially withdrawn position, andwherein at least one cavity is formed within the cavitation fluid withinthe cavitation chamber as a result of said step of retracting saidcavitation piston to said second withdrawn position; and extending thecavitation piston from the second withdrawn position, wherein saidextending step is performed until at least one cavity is imploded as aresult of said extending step.
 2. The method of claim 1, wherein saidmagnetic coupling step further comprises the step of locating a firstplurality of permanent magnets corresponding to said impeller drivesystem in proximity to a second plurality of permanent magnetscorresponding to said impeller assembly.
 3. The method of claim 1,wherein said magnetic coupling step further comprises the step oflocating a plurality of permanent magnets corresponding to a rotor ofsaid impeller assembly in proximity to an electromagnetic statorcorresponding to said impeller drive system.
 4. The method of claim 1,wherein said magnetic coupling step further comprises the step oflocating a ferromagnetic rotor of said impeller assembly in proximity toan electromagnetic stator corresponding to said impeller drive system.5. The method of claim 1, wherein said step of rotating said at leastone impeller located within the cavitation chamber is terminated priorto initiating said step of retracting said cavitation piston from saidfirst partially withdrawn position to said second withdrawn position. 6.The method of claim 1, wherein said step of rotating said at least oneimpeller located within the cavitation chamber is terminated prior toinitiating said cavitation piston extending step.
 7. The method of claim1, wherein said step of rotating said at least one impeller locatedwithin the cavitation chamber is initiated after completion of said stepof retracting said cavitation piston from said first partially withdrawnposition to said second withdrawn position.
 8. The method of claim 7,wherein said step of rotating said at least one impeller located withinthe cavitation chamber is terminated prior to initiating said cavitationpiston extending step.
 9. The method of claim 1, further comprising thestep of positioning an axis of rotation corresponding to said at leastone impeller within a horizontal plane, said positioning step performedprior to said rotating step.
 10. The method of claim 1, wherein saidstep of rotating said at least one impeller located within thecavitation chamber is performed continuously throughout said retractingand extending steps.
 11. The method of claim 1, further comprising thesteps of: terminating said rotating step; and positioning said at leastone impeller in a first position after said terminating step and priorto initiating said step of retracting said cavitation piston from saidfirst partially withdrawn position to said second withdrawn position.12. The method of claim 11, further comprising the step of determiningsaid first position on the basis of minimizing interference between saidat least one impeller and said cavitation piston.
 13. The method ofclaim 11, further comprising the step of determining said first positionon the basis of maximizing distance between said at least one impellerand said cavitation piston.
 14. The method of claim 1, furthercomprising the steps of: terminating said rotating step; and positioningsaid at least one impeller in a first position after said terminatingstep and prior to initiating said cavitation piston extending step. 15.The method of claim 14, further comprising the step of determining saidfirst position on the basis of minimizing interference between said atleast one impeller and said cavitation piston.
 16. The method of claim14, further comprising the step of determining said first position onthe basis of maximizing distance between said at least one impeller andsaid cavitation piston.
 17. The method of claim 14, wherein said step ofrotating said at least one impeller located within the cavitationchamber is initiated after said step of retracting said cavitationpiston from said first partially withdrawn position to said secondwithdrawn position.
 18. The method of claim 1, further comprising thestep of degassing the cavitation fluid prior to said first cavitationpiston retracting step.
 19. The method of claim 18, wherein saiddegassing step is performed within the cavitation chamber.
 20. Themethod of claim 19, said degassing step further comprising the step ofevacuating the cavitation chamber containing the cavitation fluid. 21.The method of claim 19, said degassing step further comprising the stepsof cavitating the cavitation fluid within the cavitation chamber toremove gas from the cavitation fluid, and periodically evacuating thecavitation chamber to remove the gas generated by the step of cavitatingthe cavitation fluid to remove gas from the cavitation fluid.
 22. Themethod of claim 21, wherein said step of cavitating the cavitation fluidto remove gas from the cavitation fluid further comprises the step ofacoustically cavitating the cavitation fluid.
 23. The method of claim21, wherein said step of cavitating the cavitation fluid to remove gasfrom the cavitation fluid further comprises the step of cavitating thecavitation fluid with said cavitation piston.
 24. The method of claim18, wherein said degassing step is performed within a degassing chamber,the method further comprising the step of filling said cavitationchamber with the cavitation fluid after completion of said degassingstep.
 25. The method of claim 24, wherein said filling step is performedby pumping the cavitation fluid from the degassing chamber to thecavitation chamber via a circulatory system.
 26. The method of claim 24,said degassing step further comprising the step of evacuating thedegassing chamber containing the cavitation fluid.
 27. The method ofclaim 24, said degassing step further comprising the steps ofacoustically cavitating the cavitation fluid within the degassingchamber to remove gas from the cavitation fluid, and periodicallyevacuating the degassing chamber to remove the gas generated by the stepof acoustically cavitating the cavitation fluid.
 28. The method of claim1, further comprising the step of reducing cross-contamination of thecavitation fluid and a hydraulic fluid within the hydraulic driver byinterposing a coupling sleeve between the cavitation chamber and saidhydraulic driver.
 29. The method of claim 28, wherein saidcross-contamination reducing step further comprises the step ofevacuating said coupling sleeve.
 30. The method of claim 1, wherein saidextending step further comprises the step of extending the cavitationpiston past the first partially withdrawn position.